The present invention relates to a side airbag device that cushions side impacts in a vehicle.
A typical side airbag device includes an inflatable airbag that deploys between a side wall of a vehicle body and an occupant sitting on a seat in the passenger compartment. When an impact that is greater than a predetermined level is applied to the side of the vehicle, gas is supplied into the airbag to near instantaneously inflate and deploy the airbag. This cushions the occupant from the impact.
Japanese Laid-Open Patent Publication No. 2006-88774 describes a side airbag device. This device is arranged in a space between the rear seat and vehicle body. More specifically, the airbag is arranged between the rear seat and the body in a folded state. The space between the rear seat and the vehicle body is hidden by a cover from the passenger compartment. During deployment the airbag is inflated toward the cover, which is made of resin and includes a thin portion. The pressure applied to the cover by the inflated airbag ruptures the thin portion. The thin portion surrounds the part of the bag through which the airbag is inflated.
In the above device, the thin portion of the cover is ruptured when the airbag is inflated, and the ruptured portion opens towards the passenger compartment so as to form an opening in the cover. The airbag is inflated in the passenger compartment through the opening of the cover. To deploy the airbag in the desired manner, each part of the thin portion in the cover must be ruptured at a predetermined timing as the airbag inflates.
However, it is difficult to rupture the entire cover in the desired manner. Particularly, as the thin portion becomes longer, proper rupturing of the thin portion becomes further difficult. If the timing at which part of the thin portion ruptures is delayed or if the cover ruptures at a part slightly separated from the thin portion during airbag inflation, the airbag and the cover would come into contact with each other in an unexpected manner. This would result in the airbag being temporarily inflated and deployed in an unexpected manner. The difficulty in rupturing the thin portion in the desired manner is one factor that interferes with proper functioning of the side airbag device.